The machinery commonly used today for making finished, headed thermoplastic tubes from 2 to 10 inches in length and from 1/2 inch to 3 inches in diameter comprises a series of machines arranged linearly and having a total process line length of about 80 to 100 feet and a total height of about 20 to 30 feet. Process lines of such dimensions are housed in factories often having several acres of floor space.
A conventional process line for producing a single type of thermoplastic tube in today's manufacturing plants includes machines for heating raw polymer material into molten plastic; extruding the molten plastic through a die to form an extruded, stretched hollow cylinder; cooling and then cutting the hollow cylinder into sleeves of equal lengths; transporting the sleeves to a machine for molding a head on one end of the sleeves to form headed tubes; transporting the headed tubes to another machine for decorating or applying a graphic to the headed tubes; transporting the printed tubes to yet another machine for applying a coating; transporting the printed tubes to a different machine for applying a cap to the headed end of the tubes and transporting the capped tubes to a final machine for unloading the tubes from the process line. The removed tubes are then packed for inventory or shipment. Such a process line requires at least four workers during operation, with one worker at the extrusion machine, at least two workers along the line to monitor the tube conveyors and other various machines and a final worker to pack the finished tubes at the end of the line.
Increasing size has dominated production equipment design in an effort to take advantage of economies associated with large scale. A conventional process line can simultaneously handle several hundred tubes in different stages of production. While some production advantages can be achieved by large size, many limitations exist, even in view of the giant size of the machinery.
Plants using conventional process lines have inherent manufacturing inefficiencies dictated by several factors such as those associated with the line machinery itself namely: large scale, mechanical operation, and process limitations as well as other inefficiencies like unit cost limitations and the number of process lines employed. Manufacturing inefficiencies, like those described below, are serious barriers which ultimately can limit the varieties of tubes available in the market.
Large scale processing machines have land, capital, and labor requirements, the costs of which are high. Additionally, large scale equipment is complex and as a result it requires more labor and higher skilled labor to operate and maintain. Most importantly, large scale design does not necessarily improve total efficiency. While production capacity may be increased, it may be done at the cost of efficiency. Complex machines require a significant amount of capital, time and labor input which can mean low overall efficiency when compared to the output.
The mechanical operation of conventional line machinery can add inefficiency to the manufacturing process. Process line down-time is inevitable because of the mechanical constraints of current machinery. For example, about 70% to 80% of line down-time is attributable to the sleeve and conveyor systems. One process line will have several transport systems, each system typically being a long chain with tube holding mandrels spaced every couple of inches, wrapped around many drive gears. These chain systems easily become jammed, frequently deliver improperly positioned articles to the process machinery and often need to be stopped for adjustment and resetting. As a result of stopping one transport system, the entire manufacturing line must be shut down.
Line down-time results in production loss. If one of the processing machines on the line malfunctions on the night shift, for example, when an engineer is not available to correct the problem, the entire line will be stopped and it will remain idle until morning. This loss is inefficient and costly to a manufacturer.
The inflexibility of the production equipment creates inherent constraints on the manufacturing process. Line equipment cannot easily be rearranged to effectuate different manufacturing processes because the individual machines weigh thousands of pounds and are not readily mobile. Furthermore, large scale machines are built for a single purpose and are limited to that purpose. For example, offset printing machines are limited to printing articles by the offset printing method. Thus the arrangement of production equipment limits the number of processing methods available to a manufacturer.
Process control for monitoring and controlling the quality of each individual tube product is not commercially available for adaption to current machinery. For example, there is no known practical way to identify, monitor, record and track defective products during the manufacturing process. Defective products are removed only at the end of the line. When a defect occurs on a tube at the beginning of the line, continued processing of that tube is inefficient since the tube will eventually be discarded.
Because an 80 to 100 foot tube production line requires at least four laborers per shift, has a predictable defect rate, requires time to retool for each job and costs money even to remain idle, it creates a high manufacturing cost that can only be lowered by large production jobs. It is a waste of resources to manufacture small numbers of tubes on such large machinery because the manufacturing cost per tube is too high. Therefore production plants can be limited to certain size manufacturing jobs in order to recapture manufacturing costs.
Today's plants for manufacturing and packing thermoplastic tubes typically house five or six process lines so that five or six different types of tubes may be made simultaneously and a single plant has at least a couple of different line layouts which create different processing methods. Unfortunately, low production costs are only achieved for large single manufacturing jobs because large volume is necessary to offset of the high cost of production inefficiencies for conventional manufacturing.